Irrigated ablation electrode having smooth edges to minimize tissue char

ABSTRACT

The invention relates to ablation catheter electrodes that solve in part the problem of tissue charring during radiofrequency ablation. The electrode assemblies of the invention include passageways that lead from the inner lumen of the assemblies to the surface of the assemblies, wherein the passageways have a smooth conjunction with the outer surface. These smooth conjunctions comprise rounded edges or are chamfered. In the case of rounded edges, the rounded edges can have fixed radii of about 0.002″ to about 0.008″.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. Non-ProvisionalUtility patent application Ser. No. 12/346,634, filed 30 Dec. 2008 (the'634 application), now U.S. Pat. No. 10,130,418, issued 20 Nov. 2018(the '418 patent), which is a continuation-in-part of internationalpatent application no. PCT/US2007/080920, filed 10 Oct. 2007 andpublished in English on 17 Apr. 2008 under international publication no.WO 2008/045925 A2 (the '920 application), designating the United Statesof America, which claims priority to U.S. Provisional Utility patentapplication Ser. No. 60/828,955, filed 10 Oct. 2006 (the '955application). The '634 application, the '920 application, and the '955application are all hereby incorporated by reference as though fully setforth herein.

BACKGROUND OF THE INVENTION a. Field of the Invention

The present invention relates to irrigated catheter assemblies. Thepresent invention further relates to ablation electrodes and assemblies,including electrode assemblies having distal irrigation fluid flow. Thepresent invention further relates to ablation electrode assemblieshaving at least one temperature sensing device and a mechanism forirrigating the ablation assembly and targeted areas. The presentinvention further relates to methods for improved assembly and accuratemeasurement and control of the electrode temperatures while effectivelyirrigating the device and target areas.

b. Background Art

Electrical stimulation of myocardial tissue controls the pumping actionof the heart. Stimulation of this tissue in various regions of the heartis controlled by a series of conduction pathways contained within themyocardial tissue. In a healthy heart, contraction and relaxation of theheart muscle (myocardium) occur in an organized fashion aselectrochemical signals pass sequentially through the myocardium fromthe sinoatrial (SA) node, which consists of a bundle of unique cellsdisposed in the wall of the right atrium, to the atrioventricular (AV)node, and then into the left and right ventricles via a route thatincludes the His-Purkinje system. The AV node is located near the ostiumof the coronary sinus in the interatrial septum in the right atrium.Each cell membrane of the SA node has a characteristic tendency of agradual leak of sodium ions over time leading to a periodic break downof the cell membrane periodically, thus allowing an inflow of sodiumions, and thereby causing the SA node cells to depolarize. The SA nodecells are in communication with the surrounding atrial muscle cells suchthat the depolarization of the SA node cells causes the adjacent atrialmuscle cells to also depolarize. This depolarization results in atrialsystole, during which the atria contract to empty and fill blood intothe ventricles. The AV node detects the atrial depolarization from theSA node and, in turn, relays the depolarization impulse into theventricles via the bundle of His and Purkinje fibers following a briefconduction delay. The His-Purkinje system begins at the AV node andfollows along the membranous interatrial septum toward the tricuspidvalve through the AV septum and into the membranous interventricularseptum. At about the middle of the interventricular septum, theHis-Purkinje system splits into right and left branches, which straddlethe summit of the muscular part of the interventricular septum.

Abnormal rhythms generally referred to as arrhythmia can occur in theheart. Cardiac arrhythmias arise when the pattern of the heartbeat ischanged by abnormal impulse initiation or conduction in the myocardialtissue. The term tachycardia is used to describe an excessively rapidheartbeat resulting from repetitive stimulation of the heart muscle.Such disturbances often arise from additional conduction pathways thatare present within the heart either from a congenital developmentalabnormality or an acquired abnormality, which changes the structure ofthe cardiac tissue, such as a myocardial infarction.

A common arrhythmia is Wolff-Parkinson-White syndrome (W-P-W). The causeof W-P-W is generally believed to be the existence of an anomalousconduction pathway or pathways that connect the atrial muscle tissuedirectly to the ventricular muscle tissue, thus bypassing the normalHis-Purkinje system. These pathways are usually located in the fibroustissue that connects the atrium and the ventricle.

Atrial arrhythmia may also occur. Three of the most common atrialarrhythmia are ectopic atrial tachycardia, atrial fibrillation, andatrial flutter. Atrial fibrillation can cause significant patientdiscomfort and even death because of a number of associated problems,including, e.g., an irregular heart rate (which causes patientdiscomfort and anxiety), loss of synchronous atrioventricularcontractions (which compromises cardiac hemodynamics, resulting invarying levels of congestive heart failure) and stasis of blood flow(which increases the likelihood of thromboembolism).

In the past, problems associated with arrhythmia have been treated withpharmacological treatment. Such treatment may not be effective in allpatients and is frequently plagued with side effects, including, e.g.,dizziness, nausea, vision problems, and other difficulties.

Alternatively, such disturbances are treated by identifying theconductive pathways and then severing part of this pathway by destroyingthese cells, which make up a portion of the pathway. Traditionally, thishas been done by either cutting the pathway surgically; freezing thetissue, thus destroying the cellular membranes; or by heating the cells,thus denaturing the cellular proteins. The resulting destruction of thecells eliminates their electrical conductivity, thus destroying, orablating, a certain portion of the pathway. By eliminating a portion ofthe pathway, the pathway may no longer maintain the ability to conduct,and the tachycardia ceases.

Catheters are a common medical tool that has been used for many years.They are employed, e.g., for medical procedures to examine, diagnose,and treat while positioned at a specific location within the body thatis otherwise inaccessible without more invasive procedures. In suchprocedures, a catheter is first inserted into a vessel near the surfaceof the body and the guided to a specific location within the body. Forexample, a catheter may be used to convey an electrical stimulus to aselected location within the human body or a catheter with sensingelectrodes may be used to monitor various forms of electrical activityin the human body.

Catheters have increasingly become a common medical procedure for thetreatment of certain types of cardiac arrhythmia. Catheter ablation isbased on the idea that by ablation (i.e., destroying) abnormal tissueareas in the heart, its electrical system can be repaired and the heartwill return to a normal rhythm. During catheter ablation, the catheteris typically inserted in an artery or vein in the leg, neck, or arm ofthe patient and then threaded, sometimes with the aid of a guide wire orintroducer, through the vessels until a distal tip of the catheterreaches the desired location for the medical procedure in the heart.

There are a number of methods used for ablation of desired areas,including for example, radiofrequency (RF) ablation. Ablation may befacilitated by transmission of energy from an electrode assembly toablate tissue at the target site. Because ablation may generatesignificant heat, which if not controlled can result in excessive tissuedamage, such as steam pop, tissue charring, and the like, it isdesirable to include a mechanism to irrigate the target area and thedevice with biocompatible fluids, such as water or saline solution. Theuse of irrigated ablation catheters can also prevent the formation ofsoft thrombus and/or blood coagulation.

Irrigated ablation catheters are cooled by passing a fluid through thecatheter during ablation. Saline irrigation is an effective way to coolthe ablation electrode and keep efficient flow around the electrode toprevent blood coagulation. Furthermore, the surface cooling that resultsfrom the saline irrigation reduces heating at the point of highestcurrent density where excessive temperatures would normally producecharring, crater formation and impedance rises (Thomas, et al., Europace6: 330-335 (2004)).

Open irrigated ablation catheters are currently the most commonirrigated catheters in the electrophysiology field. Examples of thesedevices include THERMOCOOL® by Biosense Webster and COOLPATH® by IrvineBiomedical. Closed ablation catheters usually circulate a cooling fluidwithin the inner cavity or lumen provided by the ablation electrode.Open ablation catheters typically deliver the cooling fluid through openoutlets or openings to a surface of the electrode. Open ablationcatheters use an inner cavity or lumen of the electrode, as a manifoldto distribute saline solution, or other irrigation fluids known to thoseskilled in the art, to one or more passageways that lead to anopening/outlet provided on the surface of the electrode. The coolingfluid thus flows through the outlets of the passageways onto theelectrode member. This flow through the electrode tip lowers thetemperature of the tip during operation, often making accuratemonitoring and control of the ablative process more difficult.

Using irrigated ablation catheters can prevent the impedance rise oftissue in contact with the electrode, prevent soft thrombus formation,and steam “pop” inside of the tissue while maximizing the potentialenergy transfer to the tissue, thereby allowing an increase in thelesion size produced by the ablation. Open irrigated ablation catheterscan improve the safety of RF ablation by preventing protein aggregationand blood coagulation. However, tissue char is often a problem withirrigated catheters.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to improved ablation electrodeassemblies and methods useful in conjunction with irrigated catheterdevices and other ablation catheters, wherein tissue char is minimizedduring RF ablation. Embodiments of the present invention provide anirrigated catheter having irrigation fluid directed at target areaswhere coagulation is more likely to occur so as to minimize bloodcoagulation and associated problems. The present invention includesvarious embodiments of irrigation electrode assemblies having apassageway for minimizing the blood coagulation and related problemsoccurring at or about the distal end of the electrode.

Accordingly, the present invention includes an irrigated ablationelectrode assembly. The electrode assembly has an outer surface, aninner lumen, and a proximal member. The electrode assembly furtherincludes a distal member having a distal end. The proximal member anddistal member are configured for connection with one another. Theassembly further includes at least one passageway extending from theinner lumen to the outer surface of the assembly. The at least onepassageway from the inner lumen to the outer surface has a smoothconjunction, wherein the smooth conjunction comprises a rounded edge oris chamfered. If the conjunction comprises a rounded edge, the roundededge can have a fixed radius. The fixed radius can be, for example, fromabout 0.002″ to about 0.008″. The chamfer has a width of the cutsurface, from about 0.001″ to 0.004″. The chamfer has a width of the cutsurface, from about 0.001″ to about 0.004″.

The present invention includes an alternate embodiment of an irrigatedablation electrode assembly. The electrode assembly includes a proximalmember having an outer surface and an inner lumen. The electrodeassembly further includes a distal member having an outer surface and adistal end. The proximal member and distal member are configured forconnection with one another. The assembly further includes at least oneproximal passageway extending from the inner lumen to the outer surfaceof the proximal member. The assembly further includes a distalpassageway extending from the inner lumen through the distal member tothe distal end of the electrode assembly. At least one of the distal orproximal passageways from the inner lumen to the outer surface of theproximal and/or distal member has a smooth conjunction, wherein thesmooth conjunction comprises a rounded edge or is chamfered. If theconjunction comprises a rounded edge, the rounded edge can have a fixedradius. The fixed radius can be, for example, from about 0.002″ to about0.008″. The chamfer has a width of the cut surface, from about 0.001″ toabout 0.004″. In an embodiment, the proximal passageway is separatedfrom and does not come in contact with the distal member.

The present invention further includes an alternate embodiment of anirrigated ablation electrode assembly. In an alternate embodiment, theelectrode assembly includes a proximal member having an outer surfaceand an inner lumen. The electrode assembly further includes a distalmember having an outer surface and a distal end. The proximal member anddistal member are configured for connection with one another. Theassembly further includes at least one proximal passageway extendingfrom the inner lumen to the outer surface of the proximal member. Theassembly further includes a distal passageway extending from the innerlumen through the distal member to the distal end of the electrodeassembly. At least one of the distal or proximal passageways from theinner lumen to the outer surface of the proximal and/or distal memberhas a smooth conjunction, wherein the smooth conjunction comprises arounded edge or is chamfered. If the conjunction comprises a roundededge, the rounded edge can have a fixed radius. The fixed radius can be,for example, from about 0.002″ to about 0.008″. The chamfer has a widthof the cut surface, from about 0.001″ to about 0.004″. According to thealternate embodiment, the proximal member has a lower thermalconductivity than the distal member.

The present invention further includes an alternate embodiment of anirrigated ablation electrode assembly. In an alternate embodiment, theelectrode assembly includes a proximal member having an outer surfaceand an inner lumen. The electrode assembly further includes a distalmember having an outer surface and a distal end. The proximal member anddistal member are configured for connection with one another. Theassembly further includes at least one proximal passageway extendingfrom the inner lumen to the outer surface of the proximal member. Theassembly further includes a distal passageway extending from the innerlumen through the distal member to the distal end of the electrodeassembly. At least one of the distal or proximal passageways from theinner lumen to the outer surface of the proximal and/or distal memberhas a smooth conjunction, wherein the smooth conjunction comprises arounded edge or is chamfered. If the conjunction comprises a roundededge, the rounded edge can have a fixed radius. The fixed radius can be,for example, from about 0.002″ to about 0.008″. The chamfer has a widthof the cut surface, from about 0.001″ to about 0.004″. The assemblyfurther includes an insulating member at least partially separating thedistal passageway from the distal member, wherein the insulating memberhas a lower thermal conductivity than the distal member.

The present invention further includes an alternate embodiment of anirrigated ablation electrode assembly. In an alternate embodiment, theelectrode assembly includes a proximal member having an outer surfaceand an inner lumen. The electrode assembly further includes a distalmember having an outer surface and a distal end. The proximal member anddistal member are configured for connection with one another. Theassembly further includes at least one proximal passageway extendingfrom the inner lumen to the outer surface of the proximal member. Theassembly further includes a distal passageway extending from the innerlumen through the distal member to the distal end of the electrodeassembly. At least one of the distal or proximal passageways from theinner lumen to the outer surface of the proximal and/or distal memberhas a smooth conjunction, wherein the smooth conjunction comprises arounded edge or is chamfered. If the conjunction comprises a roundededge, the rounded edge can have a fixed radius. The fixed radius can be,for example, from about 0.002″ to about 0.008″. The chamfer has a widthof the cut surface, from about 0.001″ to about 0.004″. In accordancewith an alternate embodiment, the inner lumen includes a hydrophiliccoating.

The foregoing and other aspects, features, details, utilities, andadvantages of the present invention will be apparent from reading thefollowing description and claims, and from reviewing the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A (prior art), 1B, 1C, and 1D are cross-sectional views of anablation electrode;

FIG. 2 is an isometric view of an ablation electrode according to anembodiment of the present invention;

FIG. 3 is an enlarged isometric view of the distal end of the ablationelectrode as shown in FIG. 2;

FIG. 4 is a side cross-sectional view of a distal member of an ablationelectrode according to an alternate embodiment of the present invention;

FIG. 5 is a side cross-sectional view of a distal member of an ablationelectrode according to an alternate embodiment of the present invention;

FIGS. 6, 7A, 7B, and 8 are side cross-sectional views of ablationelectrodes according to alternate embodiments of the present invention;

FIG. 9 is an illustrative view of visualized irrigation flow from anablation electrode according to an alternate embodiment of the presentinvention; and

FIG. 10 graphically depicts general bench test results for ablationelectrode assemblies in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The inventors solved the problem of undesirable tissue charring duringRF ablation by providing irrigation holes that lead from the innercavities of electrodes that have smooth or chamfered conjunctions withthe outer surface of the electrode of irrigated ablation catheters. Theinventors observed that commercially available, irrigated RF cathetersoften caused tissue char during ablation. While not desiring to be boundby any particular theory, careful observation from the inventors ledthem to believe that the rough edges of the irrigation holes were partlyresponsible for tissue char, wherein the rough edges were responsiblefor a concentration of energy intensity (“edge effects”).

In general, the instant invention relates to irrigated ablationelectrode assemblies, to catheter assemblies, as well as ablationsystems employing the irrigated ablation electrode assemblies, 110, 10and 10′, in connection with catheter assemblies. For purposes of thisdescription, similar aspects among the various embodiments describedherein will be referred to by the same reference number. As will beappreciated, however, the structure of the various aspects may differwith respect to alternate embodiments.

As generally shown in the embodiment illustrated in FIG. 2, the ablationelectrode assembly 10 may comprise part of an irrigated ablationcatheter assembly 12. The embodiments describe RF ablation electrodesand assemblies, but it is contemplated that the present invention isequally applicable to any number of other ablation electrodes andassemblies where the temperature of the device and the targeted tissuearea may be factors during the procedure.

FIG. 1A shows a prior art configuration of an ablation electrode. Theablation electrode has an electrically conductive electrode 110 thatincludes a proximal member 18, also referred to as an irrigation memberor manifold, and a distal member 20, also referred to as an ablationelectrode member. The orientation of members 18, 20 are generally suchthat distal member 20, which provides an ablation electrode or anablative surface, is situated at the distal end of assembly 110.Proximal member 18 includes an outer surface 22. Proximal member 18further includes at least one fluid or irrigation passageway 24, alsoreferred to as proximal passageway 24, that extends from an inner lumen26, to outer surface 22 of proximal member 18. In prior artconfigurations, the conjunction 70 of the irrigation passageway 24 withthe outer surface 22 of the proximal member is rough. Inner lumen 26 isin fluid communication with a fluid delivery tube (not shown). Fluidpassageways 24 of proximal member 18 and distal passageway 28 (FIG. 2)allow for increased irrigation of electrode assembly 110 during theablation of tissue.

FIG. 1B shows the improvement of the present invention. As in FIG. 1A,the ablation electrode has an electrically conductive electrode 110includes a proximal member 18, also referred to as an irrigation memberor manifold, and a distal member 20, also referred to as an ablationelectrode member. The orientation of members 18, 20 are generally suchthat distal member 20, which provides an ablation electrode or anablative surface, is situated at the distal end of assembly 110.Proximal member 18 includes an outer surface 22. Proximal member 18further includes at least one fluid or irrigation passageway 24, alsoreferred to as proximal passageway 24, that extends from an inner lumen26, to outer surface 22 of proximal member 18. The conjunction 70 of theirrigation passageway 24 with the outer surface 22 of the proximalmember 18 is smooth or chamfered. If the conjunction comprises a roundededge, the rounded edge can have a fixed radius. The fixed radius can be,for example, from about 0.002″ to about 0.008″. The chamfer has a widthof the cut surface, from about 0.001″ to about 0.004″. Inner lumen 26 isin fluid communication with a fluid delivery tube (not shown). Fluidpassageways 24 of proximal member 18 and distal passageway 28 allow forincreased irrigation of electrode assembly 110 during the ablation oftissue.

The smooth conjunction 70 is shown to closer advantage in FIG. 1C,showing an irrigation pathway 24 and the outer surface 22 of theproximal member 18. Smooth conjunction 70 can have a fixed radius. Inone embodiment, the fixed radius is about 0.002″ to 0.008″. In otherembodiments, the fixed radius is about 0.002″, about 0.003″, about0.004″, about 0.005″, about 0.006″, about 0.007″, and about 0.008″.

FIG. 1D shows another solution to minimize the edge effect, showinginstead of a smooth conjunction 70, a chamfered conjunction 70 a. Alsoshown is irrigation pathway 24 and the outer surface 22 of the proximalmember.

In accordance with another embodiment, FIG. 2 illustrates an ablationelectrode assembly 10 connected to catheter shaft 14 as part ofirrigated ablation catheter assembly 12. The assembly 12 includes atleast one fluid delivery tube 16. Ablation electrode assembly 10includes a proximal member 18, also referred to as an irrigation memberor manifold, and a distal member 20, also referred to as an ablationelectrode member. Proximal member 18 and distal member 20 are configuredto be connected together. The orientation of members 18, 20 aregenerally such that distal member 20, which provides an ablationelectrode or an ablative surface, is situated at the distal end ofassembly 10. Proximal member 18, or irrigation member, is located at theproximal end of assembly 10, although for some embodiments theorientation could be reversed.

Proximal member 18 includes an outer surface 22. Proximal member 18further includes at least one fluid or irrigation passageway 24, alsoreferred to as proximal passageway 24, that extends from an inner lumen26, for example as generally shown in FIGS. 6, 7A, 7B, and 8, to outersurface 22 of proximal member 18. The conjunction 70 of the irrigationpassageway 24 with the outer surface 22 of the proximal member 18 issmooth or chamfered. If the conjunction comprises a rounded edge, therounded edge can have a fixed radius. The fixed radius can be, forexample, from about 0.002″ to about 0.008″. The chamfer has a width ofthe cut surface, from about 0.001″ to about 0.004″. Inner lumen 26 is influid communication with fluid delivery tube 16. As can be further seenin FIGS. 3-5, distal member 20 includes a distal passageway 28 thatextends to distal end 30 of electrode assembly 10. Fluid passageways 24of proximal member 18 and distal passageway 28 allow for increasedirrigation of electrode assembly 10 during the ablation of tissue. Theconjunction 72 of the distal passageway 28 with the outer surface 74 ofthe distal member 20 is smooth or chamfered. If the conjunctioncomprises a rounded edge, the rounded edge can have a fixed radius. Thefixed radius can be, for example, from about 0.002″ to about 0.008″. Thechamfer has a width of the cut surface, from about 0.001″ to about0.004″. Proximal passageway 24 is separated from and does not come incontact with distal member 20.

Distal member 20, as shown in FIGS. 4 and 5, is generally comprised ofan electrically, and potentially thermally, conductive material known tothose of ordinary skill in the art for delivery of ablative energy totarget tissue areas. Examples of electrically conductive materialinclude gold, platinum, iridium, palladium, stainless steel, and variousmixtures and combinations thereof. In an embodiment, the distal membermay be hemispherical or semispherical in shape, although otherconfigurations may be used.

Distal member 20 may further include an inner cavity 32 for receiving aportion of proximal member 18, as further discussed below. Distal member20 further includes an aperture 34 therein forming distal passageway 28.Aperture 34 extends through distal member 20 to distal end 30 thereinproviding an opening or outlet for distal passageway 28 on the surfaceof distal member 20. Distal member 20 may further be configured with oneor more component cavities 36 for receiving and/or housing additionalcomponents within distal member 20.

As can be seen in FIG. 5, at least one temperature sensor 38, alsoreferred to as a temperature or thermal sensing device, may be providedwithin a portion (e.g., cavity 36) of distal member 20. In an alternateembodiment, two temperature sensors may be provided within cavities 36of distal member 20. Various configurations of distal member 20 mayinclude temperature sensor 38 in different locations and proximitieswithin distal member 20. In an alternate embodiment, the temperaturesensor 38 may be either partially or completely surrounded by orencapsulated by an insulation liner that is made of thermally conductiveand electrically non-conductive materials. Insulation liner 40 may beprovided in various configurations, such as provided by a tube-likeconfiguration, as shown in FIG. 5. Liner 40 may be comprised of variousmaterials, such as for example polyimide tubing.

As generally illustrated in FIG. 5, distal member 20, may furtherinclude an insulating member 42, i.e. thermal liner, disposed withinaperture 34, forming distal passageway 28 of distal member 20.Insulating member 42 may be comprised of a non and/or poor thermallyconductive material. Such material may include, but is not limited to,high-density polyethylene, polyimides, polyaryletherketones,polyetheretherketones, polyurethane, polypropylene, orientedpolypropylene, polyethylene, crystallized polyethylene terephthalate,polyethylene terephthalate, polyester, polyetherimide, acetyl, ceramics,and various combinations thereof. Insulating member 42 may be generallyprovided in a configuration that reflects the size and shape of aperture34, although the insulating member 42 generally extends to meet andconnect to inner lumen 26 of proximal member 18. Distal passageway 28 istherein created for the flow of fluid from proximal member 18, forexample, as generally shown in FIGS. 6, 7A, 7B, and 8, through distalpassageway 28 to distal end 30 of assembly 10.

An alternate embodiment of distal member 20 includes a cavity 44 forreceiving a power wire 46 (see, e.g., FIGS. 6, 7A, 7B, and 8) forconnecting distal member 20 to an energy source, such as an RF energysource. In an alternate embodiment, cavity 44 may further include a nonand/or poor thermally conductive material. Furthermore, in an alternateembodiment, power wire 46 may be soldered directly to distal member 20,or attached and/or connected to distal member 20 through the use of anadhesive or any other connection method known to one of ordinary skillin the art.

FIGS. 6, 7A, 7B, and 8 generally illustrate alternate embodiments ofelectrode assembly 10, 10′ of the present invention. As previouslydescribed, proximal member 18, 18′ and distal member 20 are configuredto be connected and/or coupled together with one another. Proximalmember 18, 18′ is comprised of a thermally nonconductive or reduced(i.e. poor) thermally conductive material that serves to insulate thefluid from the remaining portions of electrode assembly 10, inparticular distal member 20. Moreover, proximal member 18, 18′ maycomprise an electrically nonconductive material. Comparatively, overall,proximal member 18, 18′ may have lower thermal conductivity than distalmember 20. In an embodiment, proximal member 18, 18′ is made from areduced thermally conductive polymer. A reduced thermally conductivematerial is one with physical attributes that decrease heat transfer byabout 10% or more, provided that the remaining structural components areselected with the appropriate characteristics and sensitivities tomaintain adequate monitoring and control of the process. One reducedthermally conductive material may include polyether ether ketone(“PEEK”). Further examples of reduced thermally conductive materialsuseful in conjunction with the present invention include, but are notlimited to, high-density polyethylene, polyimides, polyaryletherketones,polyetheretherketones, polyurethane, polypropylene, orientedpolypropylene, polyethylene, crystallized polyethylene terephthalate,polyethylene terephthalate, polyester, polyetherimide, acetyl, ceramics,and various combinations thereof. Moreover, proximal member 18 issubstantially less thermally conductive than distal member 20. As aresult, the irrigation fluid flowing through proximal member 18 has verylittle thermal effect on distal member 20 due to the poor thermalconductivity of proximal member 18 (e.g., less than 5% effect), andpreferably nearly 0% effect. In general, characteristics anddescriptions (e.g., composition and materials) regarding proximal member18 and 18′ may be used interchangeably, among various embodiments exceptfor the specific descriptions provided regarding the design of proximalmember 18′ in accordance with the embodiment provided in FIG. 8.

The proximal member 18 may further be configured to include a couplingportion 48 that extends into inner cavity 32 of distal member 20.Proximal member 18 may be generally cylindrical in shape. Moreover, forsome embodiments, distal member 20 of ablation electrode assembly 10 mayhave a generally cylindrical shape terminating in a hemispherical distalend 30. The cylindrical shape of proximal member 18 and distal member 20may be substantially similar to one another and generally have the sameoverall diameter, which can provide or create a smooth outer body orprofile for electrode assembly 10. Distal member 20 may be configured toaccept portion 48 of proximal member 18 for attachment thereto. Thedistal member 20 may be connected by any known mechanism includingadhesives, press-fit configurations, snap-fit configurations, threadedconfigurations, or any other mechanism known to one of ordinary skill inthe art.

Proximal member 18 may further include an inner lumen 26 that isconnected to fluid delivery tube 16. The inner lumen 26 may act as amanifold or distributor for transporting and/or distributing fluidthroughout electrode assembly 10. In particular, proximal member 18 maybe configured to receive a fluid delivery tube 16 carried within atleast a portion of catheter assembly 12. Proximal member 18 includes aplurality of passageways 24. Proximal member 18 may serve as a manifoldor distributor of fluid to electrode assembly 10 through the use ofpassageways 24. Proximal passageways 24 may extend from inner lumen 26axially toward outer surface 22 of proximal member 18, wherein theconjunction 70 of the irrigation passageway 24 with the outer surface 22of the proximal member 18 is smooth or chamfered. If the conjunctioncomprises a rounded edge, the rounded edge can have a fixed radius. Thefixed radius can be, for example, from about 0.002″ to about 0.008″. Thechamfer has a width of the cut surface, from about 0.001″ to about0.004″. In an embodiment, a plurality of passageways 24 aresubstantially equally distributed around proximal member 18 to providesubstantially equal distribution of fluid to the targeted tissue areaand/or the outside of electrode assembly 10. Electrode assembly 10 maybe configured to provide a single, annular passageway 24, or a number ofindividual passageways 24 equally distributed around the proximal member18. Moreover, the passageways 24 may be generally tubular and may have aconstant diameter along the length of the passageway. Alternateconfigurations having various diameters along all or portions of thelength of the passageways may be used.

As shown in FIGS. 6, 7A, 7B and 8, proximal passageways 24 may bedirected towards or extend towards distal member 20 of electrodeassembly 10 at an angle (Θ) less than 90 degrees from the centrallongitudinal axis of proximal member 18. In an embodiment, passageways24 extends at an angle (Θ) between about 20 to about 70 degrees, and forsome embodiments, between about 30 to about 60 degrees. Alternatepositions and angles of the passageway(s) 24 may be provided inalternate embodiments of electrode assembly 10.

Distal passageway 28 is provided for and extends along the centrallongitudinal axis of proximal member 18 through distal member 20 todistal end 30 of electrode assembly 10. As shown in FIGS. 6, 7A, and 7B,distal passageway 28 may further be fully or partially surrounded by athermally non-conductive material, such as that provided by insulatingmember 42. Insulating member 42 prevents saline or any otherbiocompatible fluid from coming in contact with distal member 20.Insulating member 42 may be comprised of a thermally non-conductivematerial such as, but not limited to, high-density polyethylene,polyimides, polyaryletherketones, polyetheretherketones, polyurethane,polypropylene, oriented polypropylene, polyethylene, crystallizedpolyethylene terephthalate, polyethylene terephthalate, polyester,polyetherimide, acetyl, ceramics, and various combinations thereof.

Distal passageway 28 extends from inner lumen 26 provided by proximalmember 18. In general, the diameter of distal passageway 28 is less thanthe diameter of inner lumen 26 of proximal member 18. Accordingly, inone embodiment, inner lumen 26 and distal passageway 28 may be connectedby a tapered transition portion 50 therein providing constant fluidcommunication. The angle of the tapered transition portion may varydepending on the diameters of the inner lumen 26 and distal passageway28, as well as the length of proximal member 18. The presence of thetapered transition portion 50 between inner lumen 26 and distalpassageway 28 prevents air bubbles from being trapped inside theproximal member during fluid flow through the lumen and passageways. Inan embodiment, distal passageway 28 is slightly larger in diameter thanpassageways 24 provided by the proximal member. The diameter ofpassageways 24 and distal passageways 28 may vary depending on theconfiguration and design of electrode assembly 10. In an embodiment,distal passageway 28 includes a diameter within the range of about 0.012to about 0.015 inches, more particularly about 0.013 to about 0.014inches. In another embodiment, proximal passageways 24 include adiameter within the range of about 0.011 to about 0.014 inches, moreparticularly about 0.011 to about 0.013 inches.

In another embodiment, the inner surface of inner lumen 26 may be eithercoated with a hydrophilic coating or surface treated to create ahydrophilic surface. The treatment of inner lumen 26 with a hydrophilicsurface or coating results in another method of preventing air bubblesfrom becoming trapped inside proximal member 18. The hydrophilic coatingmaterials may include, but are not limited to, block copolymers based ofethylene oxide and propylene oxide, polymers in the polyethylene glycolfamily and silicone. For example, those materials selected from thegroup including PLURONIC® from BASF, CARBOWAX® from Dow Chemical Companyand SILASTIC MDX® from Dow Corning.

Alternate embodiments of the present invention provide the incorporationof at least one temperature sensor 38 in combination with distalpassageway 28. In particular, an embodiment, as shown in FIG. 6,includes two temperature sensors 38 provided within cavities 36 ofdistal member 20. In an alternate embodiment, as shown in FIG. 7A, onetemperature sensor is provided within a single cavity 36. Temperaturesensors may include various temperature sensing mechanisms, such as athermal sensor, disposed therein for measurement and control ofelectrode assembly 10. The temperature sensor 38 can be any mechanismknown to one of skill in the art, including for example, thermocouplesor thermistors. The temperature sensor 38 may further be surrounded, orencapsulated, by a thermally conductive and electrically non-conductivematerial, as previously discussed. This thermally conductive andelectrically non-conductive material can serve to hold temperaturesensor 38 in place within distal member 20 and provide improved heatexchange between temperature sensor 38 and distal member 20. Thismaterial may be comprised of a number of materials known to one ofordinary skill in the art, including for example, thermally conductiveresins, epoxies, or potting compounds. In yet another alternateembodiment, as shown in FIG. 7B, the distal passageway hole has roundededges 82.

In another embodiment of electrode assembly 10′, as seen in FIG. 8,proximal member 18′ includes proximal end 52 and an extended distal end54 that is received within aperture 34 of distal member 20 when proximalmember 18′ and distal member 20 are configured for connection. Distalmember 20 provides a proximal surface 56 and the surface 60 provided byinner cavity 32 that may be connected to proximal member 18′ through theuse of bonding or adhesive 58, therein coupling and/or connectingproximal member 18′ with distal member 20. Inner lumen 26′ extends fromproximal end 52 to distal end 54 of proximal member 18′. Accordinglyproximal member 18′ is configured to provide the insulating portion ofdistal passageway 28 through distal member 20. As a result, thenon-thermally conductive material of the proximal member, as previouslydescribed above, insulates distal passageway 28 through distal member20. Proximal member 18′ further includes proximal passageways 24, asdescribed above, that allow fluid flow from inner lumen 26′ to outersurface 22′ of proximal member 18′. Passageways 24 are directed towardsdistal member 20 to increase the fluid flow around the intersection ofthe proximal member to the distal member.

The flow of fluid through inner lumen 26′ provided by fluid tube 16 andultimately through proximal passageways 24 and distal passageway 28 isreflected in FIG. 8. In particular, FIG. 9 provides an irrigation flowvisualization wherein the fluid from proximal passageways 24 is directedat a 30 degree angle from the central longitudinal axis of proximalmember 18, as shown in FIG. 8. The flow visualization further shows theflow of fluid out of distal passageway 28, as shown in FIGS. 6-8, fromdistal end 30 of electrode assembly 10′.

FIG. 10 graphically depicts bench test results for ablation electrodeassemblies in accordance with an embodiment of the present invention.The purpose of the testing was to confirm that adequate temperaturecontrol was being accomplished through the use of the irrigatedelectrode including a distal passageway as the ablation system wassubjected to an overall increase in power (W) (e.g., wattage). Overall,the testing was performed using an embodiment of the present inventionwherein ablation was being performed using an electrode assembly thatmaintained irrigation flow of fluid was 13 mL/M at a perpendicularorientation to the muscle tissue being ablated. The testing showed, asreflected in FIG. 10, that an adequate temperature response wasexhibited by the ablation electrode assembly, upon the continuedincrease of power (W) provided to the ablation system. Overall, theablation electrode, as provided by the present invention, having adistal irrigation passageway was able to maintain adequate temperaturecontrol, for performing ablation, while at the same time sufficientlycooling the electrode tip. Accordingly, it is desirable to provide anirrigated ablation electrode assembly in accordance with the presentinvention that can achieve adequate temperature response within adesired range for performing ablation procedures.

As previously discussed, the ablation electrode assembly 10, 10′, 110 ofthe present invention may comprise part of an irrigated ablationcatheter assembly 12, operably connected to a pump assembly and an RFgenerator assembly which serves to facilitate the operation of ablationprocedures through monitoring any number of chosen variables (e.g.,temperature of the ablation electrode, ablation energy, and position ofthe assembly), assist in manipulation of the assembly during use, andprovide the requisite energy source delivered to the electrode assembly10, 10′, 110. Although the present embodiments describe RF ablationelectrode assemblies and methods, it is contemplated that the presentinvention is equally applicable to any number of other ablationelectrode assemblies where the temperature of the device and thetargeted tissue areas is a factor during the procedure.

In addition to the preferred embodiments discussed above, the presentinvention contemplates methods for improved measure and control of atemperature of an irrigated ablation electrode assembly 10, 10′, 110 ora target site and minimization of coagulation and excess tissue damageat and around the target site. According to one method, an ablationelectrode assembly 10, 10′, 110 is provided, having at least onetemperature sensor 38 within distal member 20 and proximal member 18 isseparate from distal member 20. An irrigation pathway 24 is providedwithin the proximal member 18 for delivery of fluid to the outer surface22 of the proximal member 18. A distal passageway 28 is further providedfor delivery of fluid to the distal end of distal member 20, therebyallowing for the benefits of irrigation of the target site and externalportions of electrode assembly 10, such as minimizing tissue damage,such as steam pop, preventing rising impedance of the ablation assembly,and minimizing blood coagulation.

Other embodiments and uses of the devices and methods of the presentinvention will be apparent to those skilled in the art fromconsideration of the specification and practice of the inventiondisclosed herein. The specification and examples should be consideredexemplary only with the true scope and spirit of the invention indicatedby the following claims. Although a number of embodiments of thisinvention have been described above with a certain degree ofparticularity, those skilled in the art could make numerous alterationsto the disclosed embodiments without departing from the spirit or scopeof this invention.

All directional references (e.g., upper, lower, upward, downward, left,right, leftward, rightward, top, bottom, above, below, vertical,horizontal, clockwise, and counterclockwise) are only used foridentification purposes to aid the reader's understanding of the presentinvention, and do not create limitations, particularly as to theposition, orientation, or use of the invention. Joinder references(e.g., attached, coupled, connected, and the like) are to be construedbroadly and may include intermediate members between a connection ofelements and relative movement between elements. As such, joinderreferences do not necessarily infer that two elements are directlyconnected and in fixed relation to each other. It is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative only and not limiting.Changes in detail or structure may be made without departing from thespirit of the invention as defined in the appended claim.

What is claimed is:
 1. An irrigated ablation electrode assemblycomprising: a distal member constructed from an electrically conductivematerial and comprising the following: an inner cavity; a distal end; anouter surface configured for delivery of ablative energy; a fluidpassageway extending from the inner cavity to the outer surface of thedistal member; and a plurality of longitudinally extending componentcavities distributed around the passageway; and at least one temperaturesensor mounted in at least one of the plurality of longitudinallyextending component cavities; wherein the fluid passageway terminates inan aperture through the distal member and the distal member outersurface; and wherein a conjunction of the fluid passageway and thedistal member outer surface is rounded or chamfered and is configured toreduce energy intensity concentration at the conjunction.
 2. Anirrigated ablation electrode assembly comprising: a distal memberconstructed from an electrically conductive material and comprising thefollowing: an inner cavity; a distal end; an outer surface configuredfor delivery of ablative energy; a fluid passageway extending from theinner cavity to the outer surface of the distal member; and a pluralityof longitudinally extending component cavities distributed around thepassageway; and at least one temperature sensor mounted in at least oneof the plurality of longitudinally extending component cavities; whereinthe fluid passageway extends axially along a central longitudinal axisof the distal member to the distal member outer surface; and wherein aconjunction of the fluid passageway and the outer surface is chamfered,the chamfer having a width of a cut surface from about 0.001 inches toabout 0.004 inches, and the conjunction being configured to reduceenergy intensity concentration at the conjunction.
 3. An irrigatedablation electrode assembly comprising: a distal member constructed froman electrically conductive material and comprising the following: aninner cavity; a distal end; an outer surface configured for delivery ofablative energy; a fluid passageway extending from the inner cavity tothe outer surface of the distal member; and a plurality oflongitudinally extending component cavities distributed around thepassageway; and at least one temperature sensor mounted in at least oneof the plurality of longitudinally extending component cavities; whereinthe fluid passageway extends axially along a central longitudinal axisof the distal member to the distal member outer surface; and wherein aconjunction of the fluid passageway and the outer surface is rounded,the conjunction having a radius of about 0.002″ to about 0.008″, and theconjunction being configured to reduce energy intensity concentration atthe conjunction.
 4. An irrigated ablation electrode assembly comprising:a distal member constructed from an electrically conductive material andcomprising the following: an inner cavity; a distal end; an outersurface configured for delivery of ablative energy; a fluid passagewayextending from the inner cavity to the outer surface of the distalmember; and a plurality of longitudinally extending component cavitiesdistributed around the passageway; at least one temperature sensormounted in at least one of the plurality of longitudinally extendingcomponent cavities; and a proximal member comprising a proximal memberouter surface, an inner lumen, and a proximal fluid passageway extendingradially outwardly from the inner lumen to the proximal member outersurface, wherein a conjunction of the proximal fluid passageway and theproximal member outer surface is rounded or chamfered and reduces energyintensity concentration at the conjunction.
 5. An irrigated ablationelectrode assembly comprising: a distal member constructed from anelectrically conductive material and comprising the following: an innercavity; a distal end; an outer surface configured for delivery ofablative energy; a fluid passageway extending from the inner cavity tothe outer surface of the distal member; and a plurality oflongitudinally extending component cavities distributed around the fluidpassageway and terminating in the distal member, wherein said pluralityof longitudinally extending component cavities comprises a firstcomponent cavity and a second component cavity; and a plurality oftemperature sensors terminating in the plurality of longitudinallyextending component cavities in the distal member, wherein the pluralityof temperature sensors comprises a first temperature sensor terminatingin the first component cavity, and a second temperature sensorterminating in the second component cavity; wherein the fluid passagewayterminates in an aperture through the distal member and the distalmember outer surface; and wherein a conjunction of the fluid passagewayand the distal member outer surface is rounded or chamfered and isconfigured to reduce energy intensity concentration at the conjunction.6. An irrigated ablation electrode assembly comprising: a distal memberconstructed from an electrically conductive material and comprising thefollowing: an inner cavity; a distal end; an outer surface configuredfor delivery of ablative energy; a fluid passageway extending from theinner cavity to the outer surface of the distal member; and a pluralityof longitudinally extending component cavities distributed around thefluid passageway and terminating in the distal member, wherein saidplurality of longitudinally extending component cavities comprises afirst component cavity and a second component cavity; and a plurality oftemperature sensors terminating in the plurality of longitudinallyextending component cavities in the distal member, wherein the pluralityof temperature sensors comprises a first temperature sensor terminatingin the first component cavity, and a second temperature sensorterminating in the second component cavity; wherein the fluid passagewayextends axially along a central longitudinal axis of the distal memberto the distal member outer surface; and wherein a conjunction of thefluid passageway and the outer surface is chamfered, the chamfer havinga width of a cut surface from about 0.001 inches to about 0.004 inches,and the conjunction being configured to reduce energy intensityconcentration at the conjunction.
 7. An irrigated ablation electrodeassembly comprising: a distal member constructed from an electricallyconductive material and comprising the following: an inner cavity; adistal end; an outer surface configured for delivery of ablative energy;a fluid passageway extending from the inner cavity to the outer surfaceof the distal member; and a plurality of longitudinally extendingcomponent cavities distributed around the fluid passageway andterminating in the distal member, wherein said plurality oflongitudinally extending component cavities comprises a first componentcavity and a second component cavity; and a plurality of temperaturesensors terminating in the plurality of longitudinally extendingcomponent cavities in the distal member, wherein the plurality oftemperature sensors comprises a first temperature sensor terminating inthe first component cavity, and a second temperature sensor terminatingin the second component cavity; wherein the fluid passageway extendsaxially along a central longitudinal axis of the distal member to thedistal member outer surface; and wherein a conjunction of the fluidpassageway and the outer surface is rounded, the conjunction having aradius of about 0.002″ to about 0.008″, and the conjunction beingconfigured to reduce energy intensity concentration at the conjunction.8. An irrigated ablation electrode assembly comprising: a distal memberconstructed from an electrically conductive material and comprising thefollowing: an inner cavity; a distal end; an outer surface configuredfor delivery of ablative energy; a fluid passageway extending from theinner cavity to the outer surface of the distal member; and a pluralityof longitudinally extending component cavities distributed around thefluid passageway and terminating in the distal member, wherein saidplurality of longitudinally extending component cavities comprises afirst component cavity and a second component cavity; and a plurality oftemperature sensors terminating in the plurality of longitudinallyextending component cavities in the distal member, wherein the pluralityof temperature sensors comprises a first temperature sensor terminatingin the first component cavity, and a second temperature sensorterminating in the second component cavity; a proximal member includinga central longitudinal axis and comprising a proximal member outersurface, an inner lumen, and a proximal fluid passageway extendingradially outwardly from the inner lumen to the proximal member outersurface; wherein a conjunction of the proximal fluid passageway and theproximal member outer surface is rounded or chamfered and reduces energyintensity concentration at the conjunction.